Memory card

Abstract

A memory card of the present invention serves as a reusable prepaid card. In the memory card, prepaid-money data is stored in a user memory constituted of a flash erase type EEPROM, and decreased as the card is used. When the prepaid-money data becomes zero, the user memory is initialized for reuse. The memory card includes an EPROM to which data of a predetermined number of times of initialization is preset and which decreases in data of the number of times of initialization and an initialization control logic for executing initialization in response to an initialization command until data of the EPROM becomes zero, and inhibiting the initialization even though the initialization command is input when the data becomes zero.

What is claimed is: 
     
       1. A memory card comprising: memory means capable of being initialized;   means for counting the number of times said memory means is initialized, the counting means being an externally inaccessible counting means; and   initialization means for initializing said memory means upon receiving an initialization command only when the number of times counted by said counting means is smaller than a predetermined value, initializing of said memory means being inhibited when the number of times counted by said counting means is equal to or larger than a predetermined value.   
     
     
       2. The memory card according to claim 1, in which said memory means includes a flash erase type EEPROM. 
     
     
       3. The memory card according to claim 1, in which said memory means includes a flash erase type EEPROM having a large number of memory cells, a predetermined number of memory cells of said large number of memory cells being set to a first level in an initial state and changed in sequence from the first level to a second level, and said initializing means simultaneously changes levels of said predetermined number of memory cells to the first level.   
     
     
       4. The memory card according to claim 1, in which said counting means includes an EPROM whose data is rewritten every initialization of said memory means. 
     
     
       5. The memory card according to claim 1, in which said counting means includes a large number of fuses, and one of said large number of fuses is cut off every initialization of said memory means. 
     
     
       6. The memory card according to claim 1, in which said counting means includes a counter which is cleared before a first initialization of said memory means starts and which counts up every initialization of said memory means. 
     
     
       7. The memory card according to claim 1, in which said memory means stores prepaid money data. 
     
     
       8. The memory card according to claim 1, in which said counting means includes a wired logic circuit, and said initialization control means includes a logic gate for supplying the initialization command to said initializing means, said logic gate being rendered nonconductive when the number of times of initialization amounts to the predetermined value. 
     
     
       9. A memory card comprising: memory means capable of being initialized;   means for storing a key necessary for initializing said memory means;   means for verifying whether a key input by an operator coincides with the key stored in said storing means;   means for counting the number of times said memory means is initialized, the counting means being an externally inaccessible counting means; and   initialization means for initializing said memory means upon receiving an initialization command only when the number of times counted by said counting means is smaller than a predetermined value, initializing of said memory means being inhibited when the number of times counted by said counting means is equal to or larger than a predetermined value.   
     
     
       10. The memory card according to claim 9, in which said memory means includes a flash erase type EEPROM. 
     
     
       11. The memory card according to claim 9, in which said memory means includes a flash erase type EEPROM having a large number of memory cells, a predetermined number of memory cells of said large number of memory cells being set to a first level in an initial state and changed in sequence from the first level to a second level, and said initializing means simultaneously changes levels of said predetermined number of memory cells to the first level.   
     
     
       12. The memory card according to claim 9, in which said counting means includes an EPROM whose data is rewritten every initialization of said memory means. 
     
     
       13. The memory card according to claim 9, in which said counting means includes a large number of fuses, and one of said large number of fuses is cut off every initialization of said memory means. 
     
     
       14. The memory card according to claim 9, in which said counting means includes a counter which is cleared before a first initialization of said memory means starts and which counts up every initialization of said memory means. 
     
     
       15. The memory card according to claim 9, in which said memory means stores prepaid money data. 
     
     
       16. The memory card according to claim 9, in which said counting means includes a wired logic circuit, and said initialization control means includes a logic gate for supplying the initialization command to said initializing means, said logic gate being rendered nonconductive when the number of times of initialization amounts to the predetermined value.